1. Field of the Invention
The present invention relates to a pixel structure and a method of forming the same, and more particularly, to a pixel structure and a method of forming the same that improves the image flicker phenomena of the display panel.
2. Description of the Prior Art
The traditional cathode ray tube (CRT) displays have been gradually replaced by the flat displays. Among the flat displays, the liquid crystal display (LCD) is a most popular flat display and widely used nowadays, and the LCD has advantages such as low weight, low power consuming and low driving voltage and can be integrated into and applied to daily products such as notebooks, digital cameras, video game machines. In the design of pixel structure of the conventional LCDs, it is a main industrial development trend to adopt thin film transistors as the driving devices. Generally speaking, the coupling capacitor effect may occur between the conductive layers of the thin film transistor and the conductive layers of other adjacent components so that the display panel will have the problem such as image flicker phenomena when displaying. With reference to FIG. 1 and FIG. 2, FIG. 1 is a top view schematic diagram illustrating a part of the pixel structure of the conventional display panel, and FIG. 2 is a cross-sectional schematic diagram of the pixel structure along the line A-A′illustrated in FIG. 1. As shown in FIG. 1 and FIG. 2, FIG. 1 and FIG. 2 illustrate the pixel structure of the conventional display panel, wherein the pixel structure 10 of the conventional display panel is defined by a source line 11 and a gate line 12, and includes a substrate 13, the source line 11, a source electrode 14, the gate line 12, and a gate electrode 15 disposed on the substrate 13, a gate dielectric layer 16 covering and disposed on the gate line 12 and the gate electrode 15, a drain electrode 17 and a drain shielding extension 18 disposed on the gate dielectric layer 16, a protection layer 19 disposed on the drain electrode 17, the drain shielding extension portion 18 and the gate dielectric layer 16, and a transparent electrode 20 disposed on the protection layer 19. However, in the pixel structure 10 of the conventional display panel, a parallel capacitor named as the first coupling capacitor Cgd1 occurs in the vertically overlapping area of the drain electrode 17 and the gate electrode 15. In another aspect, the drain shielding extension portion 18 and the adjacent gate line 12 are parallel to each other and the gate dielectric layer 16 and the insulating protection layer 19 are disposed between the drain shielding extension portion 18 and the adjacent gate line 12, so as to form a lateral capacitor named as the second coupling capacitor Cgd2. The capacitance of the first coupling capacitor Cgd1 is substantially proportioned to the overlapping area A of the drain electrode 17 and the gate electrode 15 in the vertical direction, and the capacitance of the second coupling capacitor Cgd2 is substantially proportioned to the laterally overlapping area of the drain shielding extension portion 18 and the gate line 12 and is substantially in reverse proportion to the straight distance P between the drain shielding extension portion 18 and the gate line 12. Conventionally, the design of thin film transistor channel of pixel structures of the conventional large-size LCD panel is large. As a result, if only the first coupling capacitor Cgd1 formed in the overlapping area A of the gate electrode 15 and the drain electrode 17 in the vertical direction is considered and listed for calculation, the influence upon the deviation of the total coupling capacitance is small oppositely. On the contrary, in the design of the pixel structure of small-size or middle-size LCD panels, since the channel width of the thin film transistor is shortened obviously, the signal interference resulted from the second coupling capacitor Cgd2 will become obvious when the pixel structure of the display panel being operated so that the flicker phenomena of the display panel will become seriously and can not be ignored.
Form the above description, the pixel structure of the conventional LCD panel has a high coupling capacitor effect, such that the display panel easily has the flicker phenomena when displaying images. Consequently, to develop a display panel pixel structure having low flicker phenomena is an important research object for display industry.